Java HashSet iterator() Method

The HashSet.iterator() method in Java is used to obtain an iterator over the elements in a HashSet. This guide will cover the method’s usage, explain how it works, and provide examples to demonstrate its functionality.

Table of Contents

1. Introduction
2. iterator Method Syntax
3. Examples
   • Iterating Over a HashSet
   • Removing Elements While Iterating
4. Conclusion

Introduction

The HashSet.iterator() method is a member of the HashSet class in Java. It allows you to traverse the elements in a HashSet sequentially. The iterator provides methods to check for the next element and to retrieve and remove elements during the iteration.

iterator Method Syntax

The syntax for the iterator method is as follows:

public Iterator<E> iterator()

• The method does not take any parameters.
• The method returns an Iterator<E> over the elements in the HashSet.

Examples

Iterating Over a HashSet

The iterator method can be used to iterate over the elements in a HashSet.

Example

import java.util.HashSet;
import java.util.Iterator;

public class IteratorExample {
    public static void main(String[] args) {
        // Creating a HashSet of Strings
        HashSet<String> languages = new HashSet<>();

        // Adding elements to the HashSet
        languages.add("Java");
        languages.add("Python");
        languages.add("C");

        // Obtaining an iterator
        Iterator<String> iterator = languages.iterator();

        // Iterating over the HashSet
        System.out.println("HashSet elements:");
        while (iterator.hasNext()) {
            String language = iterator.next();
            System.out.println(language);
        }
    }
}

Output:

HashSet elements:
Java
C
Python

Removing Elements While Iterating

You can use the iterator to remove elements from the HashSet while iterating.

Example

import java.util.HashSet;
import java.util.Iterator;

public class RemoveWhileIteratingExample {
    public static void main(String[] args) {
        // Creating a HashSet of Strings
        HashSet<String> languages = new HashSet<>();

        // Adding elements to the HashSet
        languages.add("Java");
        languages.add("Python");
        languages.add("C");

        // Obtaining an iterator
        Iterator<String> iterator = languages.iterator();

        // Removing elements while iterating
        while (iterator.hasNext()) {
            String language = iterator.next();
            if (language.equals("Python")) {
                iterator.remove();
            }
        }

        // Printing the HashSet after removal
        System.out.println("HashSet after removing Python: " + languages);
    }
}

Output:

HashSet after removing Python: [Java, C]

Conclusion

The HashSet.iterator() method in Java provides a way to traverse and manipulate the elements in a HashSet. By understanding how to use this method, you can efficiently iterate over collections and perform operations such as removing elements during iteration. This method is particularly useful for scenarios where you need to process each element in the set sequentially.